الفهرس 
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Abstract
The present study was carried out at a private poultry farm under supervision of Animal Production Department, Faculty of Agriculture, Tanta University, during the period from April to May 2016. This study was carried out to study the influence of dietary vitamin C with or without organic selenium on performance, some physiological parameters and some carcass and bone traits of broilers A total of 360 one-day-old unsexed Hubbard broilers chicks were used in this experiment. Birds were wing-banded, individually weighed to the nearest gram, and randomly distributed into four experimental groups; with three replicates of 30 chicks each. The average initial body weights of the treatments groups were nearly similar with no significant differences. The basal diet was a commercial corn-soybean meal diet formulated to meet or exceed the nutritional requirement of growing chicks as recommended by the NRC (1994). Dietary treatments evaluated included: T1 Basal diet without any addition (Cont.) T2 Basal diet plus 100 mg/kg vitamin-C (Vit C) T3 Basal diet supplemented with 0.5 mg/kg Organic selenium (Se) T4 Basal diet containing 0.5 mg/kg Organic selenium treated with 100 mg/kg vitamin-C (vit C+ Se) Measurements: 1- Performance Trails Body weight and weight gain, feed consumption, feed conversion ratio, mortality rate. 2- carcass and bone traits Relative weight of carcass and internal organs , dressing percentage, fat percentage, bone resistance and bone composition 3- Biochemical Analysis of Blood Serum Total protein, albumin, globulin, total lipids, triglyceride, total cholesterol, aspartate transaminase (AST), alanine transaminase (ALT) Obtained results could be summarized as follows: Through the whole experiment period), birds fed diet the vitamin with the element (Vit C+Se) recorded the significantly higher body weight gain compared with control ones by 109.69% followed by those fed the vitamin only (Vit C) which was significantly higher body weight gain by 103.82% then the element group (Se) supplementation which was significantly higher body weight gain by 103.08% than the control group During the period from 2 to 5 weeks of age, feed consumption of birds fed the experimental diets consumed significantly less feed compared to control ones. There were no significant differences among birds fed the vitamin, the element and the mixture of them. Feed consumption was higher in ( Se ) group followed by (Vit C) then (Vit C + Se). During the whole experimental period, birds fed the vitamin and the element (Vit C+ Se) had significantly better feed conversion ratio compared to control ones, followed by the vitamin group (Vit C) then the element ones (Se). Generally, the improvement in feed conversion ratio may be related to higher growth rate of the Vit C+ Se group as compared to control or other experimental groups. Mortality percent of birds fed the mixture of vitamin C and selenium ( Vit C+Se) or which fed selenium (Se) had little mortality percentage compared to vitamin C (Vit C) or control groups, but the differences were not significant. In respect to the relative carcass weight, the highest value ( 108.53 % of the control) was noticed in birds fed the mixture of vitamin C and selenium followed by birds fed the vitamin C only ( 106.08 %) then birds fed selenium only (104.25 %) compared to control group. The same trend was observed in the relative dressing and breast weight; the highest relative weight was in the birds fed the mixture of vitamin C and selenium followed by the birds fed vitamin C only then the birds fed selenium only compared to control ones. About the internal organs, some of them (liver, thymus and spleen) were significantly affected by fed selenium, vitamin C and their mixture, while other of them (gizzard, heart and bursa) were not significantly affected. The highest relative weights of liver, thymus and spleen was in birds fed the mixture of vitamin C and selenium followed by the birds fed vitamin C only then the birds fed selenium only compared to control ones. Bone-breaking strength was significantly increased when vitamin C , selenium or the mixture of them was supplemented in the diets. Chemical composition of tibia bone showed significantly higher values of crude ash, calcium, and phosphorus percentages with the mixture of vitamine C and selenium, followed with vitamin C, then selenium treatment comparing to control group. Both of total protein and globulin concentrations were increased in all treatments compared to control group. The birds received the mixture of vitamin C with selenium recorded higher value followed by birds received vitamin C only then the birds which received selenium only, compared to the control. Birds fed on both Vitamin C with selenium shows the lowest value of total lipids, total cholesterol and triglyceride followed by birds received the vitamin (Vit C) or selenium (Se) compared to the control group. Activity of liver enzymes (ALT and AST) were not statistically affected in birds supplemented by Vitamin C, selenium or the mixture of them compared with control group.